This invention relates to the improvement of a digital broadcast receiving device used in a digital broadcasting system.
Recently, the digital signal processing techniques for video and audio signals have markedly progressed and various systems are developed in various countries in the world to attain digital broadcasting services and a combination of the broadcasting and communication. Among them, the most important technique is the compression technique for video and audio signals. As the compression technique, MPEG, JPEG, H.261 are mainly used, for example. Particularly, the compression technique proposed by ISO/IEC13818-1 (Moving Picture Coding Experts Group (ISO/IEC JTC1/SC29/WG11)) is studied for international standardization of the broadcasting, communication and storage media.
In the ISO/IEC13818-1, not only a compressed video signal but also bit streams compressed for each data, audio signal and video signal of a program are multiplexed and broadcast and the content of a control portion for receiving a specified program is fixedly determined on the receiver side.
The multiplex control for bit streams in the broadcasting and communication of ISO/IEC13818-1 is briefly explained with reference to FIGS. 1 and 2.
FIG. 1 shows models of a video-i system and video-2 system in a packet forming method, and video data and audio data are first divided into one-frame units and headers are attached to the respective units to constitute PES (Packetized Elementary Stream). The length of PES is variable. Further, in order to multiplex video data and audio data on the time base, each PES is basically divided for every 184 bytes to make packets and a header of 4 bytes is added to each packet to make a TP (Transport Packet) of 188 bytes. FIG. 1 shows a case wherein video data and audio data are multiplexed, but in practice, added data of a program and data such as program information are formed into a TP form and multiplexed on the time base.
Next, a method for constructing a bit stream for broadcasting is explained with reference to FIG. 2.
In FIG. 2, programs A, B indicate one program, and they are output as TS(A), TS(B) in which a video-2 system, audio-2 system, ECM (Entitlement Control Messages)-1 system and program map table (PMT: Program Map Table) supplied for each program are multiplexed by multiplexing devices 1, 2. In this case, video, audio and ECM respectively indicate video data, audio data and added information data and PMT contains a packet ID for identifying video data, audio data and added information data and a description relating to the program. In TS(A), TS(B) of the programs A, B, a program association table (PAT), network information table (NIT), conditional access table (CAT), individual user key information (EMM (Entitlement Management Messages) information) which is necessary for watching and listening to the program and is supplied to the individual receiver and the like are multiplexed and output as a TS corresponding to transfer channel data.
In the above digital broadcasting system, in order to simplify the watching and listening management of subscribers, individual user key information is periodically updated on the transmitter side. Therefore, in order to rapidly start the watching and listening operation when the standby state is changed over to the watching and listening state, it is necessary to monitor the updating operation of the individual user key information on the receiver side. In this case, the troublesome condition can be coped with by maintaining the sub-power supply for a necessary circuit such as a processor for managing the individual user key information in the ON state, but this will wastefully consume power.
As described above, if a method for maintaining the sub-power supply for a necessary circuit in the ON state is used to monitor the updating of added information on the receiver side in a case where added information such as individual user key information is periodically updated in a digital broadcasting system, power will be wastefully consumed.
An object of this invention is to provide a digital broadcast receiving device capable of updating added information while the power consumption is suppressed to minimum in the standby mode when digital broadcast in which added information is periodically updated is received and rapidly starting the watching and listening operation when the standby state is changed over to the watching and listening state.
A digital broadcast receiving device according to this invention comprises a first processor for extracting at least added information containing mail information or information used for watching and listening to a program and multiplexed on a digital broadcast signal from the broadcast signal; storage means for storing added information; and a second processor having a low power consumption mode and a normal power mode, for effecting the circuit control for the watching and listening operation according to a preset program and added information; wherein the first processor extracts the added information which meets a predetermined filter condition from the digital broadcast signal and informs the second processor that the added information is extracted, and the second processor is set into the low power consumption mode when the device is set in the standby state, and changed over to the normal power mode from the low power consumption mode when it is informed from the first processor that the added information is extracted, then the second processor transfers and writes the added information extracted by the first processor into the storage means after it is changed into the normal power mode, and is returned to the lower power consumption mode again after the writing operation of the added information is completed.
With the above construction, when the first processor extracts added information for watching and listening to the program from a digital broadcast signal in the standby state, it informs the second processor that the added information is extracted. Then, the second processor is changed over from the low power consumption mode to the normal power mode, transfers and stores the added information from the first processor into the storage means, and is then returned to the low power consumption mode again after completion of the storage of the added information.
As a result, since the second processor detects the added information in the standby state and is operated in the normal power mode only when the added information is stored into the storage means, the added information can be updated while the power consumption is suppressed to minimum, thereby permitting the watching and listening operation to rapidly start when the standby state is changed over to the watching and listening state.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.